Hollow Earth Theory...writing a book on it?

Sounds like you're a bit too heavily influenced by your source, but I had an idea way back when I was eleven with a 'hollow earth' premise. See, I always thought it was so sad that animals went extinct because of human impact on the earth, so I came up with this idea of a mive zoo of every animal humans could ever capture under the crust. (There were also extinct plants). The lava was somehow channelled in rock pages to form a heating system. All the (secretly) smartest people in the world lived there, so technology was way advanced. People were often whisked away from their boring surface lives to help. Do with that plotholed, half-formed thing what you will.